Thank you for your query.
Following use of Augmentin
one can have loose motions which has happened in your son's case. Rash
can also follow use of this antibiotic. I suggest that you give your son some probiotics which shall help in his intestines to settle down. You can also give him buttermilk. For rash you can apply any bland ointment and observe for a day if it resolves.
I hope I have answered your query to your satisfaction.
Wishing your son an early recovery.
Rajiv K Khandelwal